1. Field of the Invention
The present invention relates to data recording and reproducing apparatus, data recording and reproducing method, and program therefor capable of receiving audio data created by encoding an original sound signal and decoding the audio data back to the original sound signal to thereby reproduce the original sound signal.
2. Description of the Related Art
As digital consumer electronics and personal computers have spread in recent years, a usage including recording analog TV broadcasts, digital TV broadcasts, radio broadcasts, and others on recording media in the form of disks or cards and reproducing them is enjoying wider acceptance. Under these circumstances, there is an increasing demand for capabilities of viewing and listening to recorded contents in shorter times. In response to the demand, various kinds of variable speed reproduction methods have been devised. In one method, data about video or audio are thinned out at simple constant intervals. In another method, data are thinned out at non-constant intervals corresponding to features possessed by video and audio contents.
A digest reproduction technique is disclosed which plays back summarized contents at high speed by classifying reproduced data having a title to be reproduced into 3 kinds of intervals: for example, silent interval, musical signal interval, and vocal signal interval, according to features possessed by sounds of the reproduced contents, and reproducing the contents while selecting vocal signal intervals preferentially (see, for example, patent reference 1). In this patent reference 1, a technique for performing FFT (fast Fourier transform) processing before the audio input signal is compressed and encoded is proposed. In particular, energies in frequency bands are observed. Features in the subintervals are classified. Furthermore, patent reference 1 proposes a technique for classifying features possessed by subintervals by decoding data encoded by MPEG (Moving Picture Experts Group) audio technology to create subband data and observing energies possessed by the subbands.
In the method described in this patent reference 1, when an analog audio input signal, for example, is simply encoded, multiplexed with the video signal, and recorded on a recording medium such as a hard disk, feature points of the contents can be extracted. When summarized contents are reproduced later, information about the feature points can be utilized. Alternatively, when a digital multiplexed data stream sent in, for example, by a digital broadcast may be once separated and decoded. The resulting data may be reencoded and remultiplexed. Then, the data are recorded on a recording medium. At this time, feature points of the contents may be extracted and stored. When summarized contents are reproduced later, information about the feature points may be utilized.
In the method of JP-A-10-247093 (paragraphs [0008] and [0009]), however, the following problem occurs in a case where a digital multiplexed data stream sent in by a digital broadcast is once separated and decoded. The resulting data are reencoded and remultiplexed, and then recorded on a recording medium. Where features of voice are classified from encoded audio data, the amount of computation is increased because the data are decoded and subband data are created. This increases the burden on the apparatus.
Furthermore, in the method of JP-A-10-247093, another problem takes place in a case where other data (e.g., a different TV program) on a recording medium are reproduced while a digital multiplexed data stream sent in, for example, by a digital broadcast is concurrently being recorded on the recording medium without modifying the format. In the method of JP-A-10-247093, the data stream is decoded to extract feature points. During reproduction, the decoder is occupied by the processing for decoding the stream of the other data. Therefore, it may be impossible to extract feature points possessed by the currently recorded contents in real time. Consequently, there is the problem that where summarized contents of the recorded data are reproduced, it may not be possible to perform digest reproduction corresponding to the features possessed by the contents.
The “digest reproduction” referred to above means that summarized contents of data are reproduced. In addition, the “digest reproduction” means that contents are partially omitted and reproduced in a shorter time than usual.
In view of the foregoing circumstances, it is desirable to provide data recording and reproducing apparatus, data recording and reproducing method, and program therefor capable of extracting feature points of the contents of data without increasing the amount of computation.
It is also desirable to provide a technique which, when other data are being reproduced during recording of audio data, is capable of extracting feature points of the contents of the data being recorded.